I know this won't work. I tried it in various forms and failed all times. What is the simplest way to achieve the following result?
ALTER TABLE XYZ AUTO_INCREMENT = (select max(ID) from ABC);
This is great for automation projects.
SELECT @max := (max(ID)+1) from ABC; 开发者_StackOverflow -> This works!
select ID from ABC where ID = (@max-1); -> This works!
ALTER TABLE XYZ AUTO_INCREMENT = (@max+1); -> This fails :( Why?
Use a prepared statement:
SELECT @max := MAX(ID)+ 1 FROM ABC;
PREPARE stmt FROM 'ALTER TABLE ABC AUTO_INCREMENT = ?';
EXECUTE stmt USING @max;
DEALLOCATE PREPARE stmt;
Following the MySQL documentation, this worked for me in MySQL 5.7:
SET @m = (SELECT MAX(id) + 1 FROM ABC);
SET @s = CONCAT('ALTER TABLE XYZ AUTO_INCREMENT=', @m);
PREPARE stmt1 FROM @s;
EXECUTE stmt1;
DEALLOCATE PREPARE stmt1;
Whoever is having a problem with PREPARE stmt FROM 'ALTER TABLE XYZ AUTO_INCREMENT = ?' can use:
CREATE PROCEDURE reset_xyz_autoincrement
BEGIN
SELECT @max := MAX(ID)+ 1 FROM ABC;
set @alter_statement = concat('ALTER TABLE temp_job_version AUTO_INCREMENT = ', @max);
PREPARE stmt FROM @alter_statement;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END
I'm creating an automated database transformation script for a new version of my application.
In one table, I needed to change the primary auto-increment field to a different field. Since this page came up first many times while I googled a solution for it, here's a solution that eventually worked for me:
-- Build a new ID field from entry_id, make it primary and fix the auto_increment for it:
ALTER TABLE `entries` ADD `id` INT UNSIGNED NOT NULL FIRST;
UPDATE entries SET id = entry_id;
ALTER TABLE `entries` ADD PRIMARY KEY ( `id` );
-- ...the tricky part of it:
select @ai := (select max(entry_id)+1 from entries);
set @qry = concat('alter table entries auto_increment=',@ai);
prepare stmt from @qry; execute stmt;
-- ...And now it's possible to switch on the auto_increment:
ALTER TABLE `entries` CHANGE `id` `id` INT( 10 ) UNSIGNED NOT NULL AUTO_INCREMENT;
Reset Auto Increment IDs.
Reset Auto Increment IDs
Update all auto increment columns in a database to the smallest possible value based on current values in the databases. We needed to do this after cleaning out a database.
Use a prepared statement within a stored procedure:
drop PROCEDURE if exists reset_autoincrement;
DELIMITER //
CREATE PROCEDURE reset_autoincrement (IN schemaName varchar(255))
BEGIN
DECLARE done INT DEFAULT FALSE;
DECLARE o_name VARCHAR(255);
DECLARE o_table VARCHAR(255);
DECLARE cur1 CURSOR FOR SELECT COLUMN_NAME, TABLE_NAME FROM information_schema.`COLUMNS` WHERE extra LIKE '%auto_increment%' and table_schema=schemaName;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
OPEN cur1;
read_loop: LOOP
FETCH cur1 INTO o_name, o_table;
IF done THEN
LEAVE read_loop;
END IF;
set @qry1 = concat('SELECT MAX(`',o_name,'`) + 1 as autoincrement FROM `',o_table,'` INTO @ai');
PREPARE stmt1 FROM @qry1;
EXECUTE stmt1;
IF @ai IS NOT NULL THEN
SELECT o_name, o_table;
select @qry1;
select @ai;
set @qry2 = concat('ALTER TABLE `',o_table,'` AUTO_INCREMENT = ', @ai);
select @qry2;
PREPARE stmt2 FROM @qry2;
EXECUTE stmt2;
END IF;
END LOOP;
CLOSE cur1;
END //
DELIMITER ;
call reset_autoincrement('my_schema_name');
Personally I'd probably use either a shell script or a little C#/C++ application or PHP/Ruby/Perl script to do this in 2 queries:
- Grab the value you want
SELECT MAX(ID) FROM ABC;
- Alter the table using the value
ALTER TABLE XYZ AUTO_INCREMENT = <insert value retrieved from first query here>
Obviously being careful that the new auto increment won't cause any key clashes with existing data in the XYZ
table.
Ok guys. I have come up with a not so intuitive solution. The best part is that it works!
SELECT @max := max(ID) from ABC;
ALTER TABLE XYZ AUTO_INCREMENT = 1;
ALTER TABLE XYZ ADD column ID INTEGER primary key auto_increment;
UPDATE XYZ SET ContactID = (ContactID + @max);
If you really want to do this in MySQL alone, you can just dump the dynamically built alter command to a file on disk and then execute it.
Like so:
select concat('ALTER TABLE XYZ AUTO_INCREMENT = ',max(ID)+1,';') as alter_stmt
into outfile '/tmp/alter_xyz_auto_increment.sql'
from ABC;
\. /tmp/alter_xyz_auto_increment.sql
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